A possible unified mechanism of like and unlike chain-end stereocontrol for primary propene-coordinated polymerizations

Giuseppe Milano, Giuseppe Fiorello, Gaetano Guerra*, Luigi Cavallo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Theoretical studies relative to propene primary insertion for polymerization catalysts based on Brookhart-type Ni(II) and biscylopentadienyl Ti(IV) complexes are reported. On the basis of geometrical considerations relative to calculated transition states, a unified-mechanism for like (isospecific) and unlike (syndiospecific) chain-end stereo-control for primary propene polymerizations, which can be considered as a sub-case of the more general mechanism of the chiral orientation of the growing chain, is suggested. As usual, the selection between monomer enantiofaces would be determined by the conformation relative to the Mt-C bond (negative or positive values of θ1), which for these catalysts would be determined by the configuration of the tertiary carbon bond of the growing chain being closest to the metal, but would also be critically depending on the conformation of the first C-C bond of the chain. In particular, chain-end stereo-controlled polymerization catalysts imposing that the first tertiary H atom would point toward the metal θ2H≈0°) or toward the monomer (θ2H≈100°) would lead to preference for isospecific and syndiospecific propagation, respectively.

Original languageEnglish (US)
Pages (from-to)1564-1572
Number of pages9
JournalMacromolecular Chemistry and Physics
Volume203
Issue number10-11
DOIs
StatePublished - Jul 29 2002

Keywords

  • Poly(propylene) (PP)
  • Quantum chemistry
  • Ziegler Natta polymerization

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

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